file: Fix regression in fsnotify code

This was a major deadlock that hit the file resource. I didn't notice it
earlier because I was using an older version of fsnotify and I hadn't
done a go get -u to refresh it. I finally tracked this down, and will
vendor the repository until a fix upstream or a workaround downstream is
added.

The upstream issue is: https://github.com/fsnotify/fsnotify/issues/123

.gitmodules

@@ -7,3 +7,6 @@
 [submodule "vendor/github.com/grpc-ecosystem/grpc-gateway"]
 	path = vendor/github.com/grpc-ecosystem/grpc-gateway
 	url = https://github.com/grpc-ecosystem/grpc-gateway
+[submodule "vendor/gopkg.in/fsnotify.v1"]
+	path = vendor/gopkg.in/fsnotify.v1
+	url = https://gopkg.in/fsnotify.v1

README.md

@@ -30,7 +30,7 @@ If you have a well phrased question that might benefit others, consider asking i
 * Clone the repository recursively, eg: `git clone --recursive https://github.com/purpleidea/mgmt/`.
 * Get the remaining golang dependencies on your own, or run `make deps` if you're comfortable with how we install them.
 * Run `make build` to get a freshly built `mgmt` binary.
-* Run `time ./mgmt run --file examples/graph0.yaml --converged-timeout=1` to try out a very simple example!
+* Run `time ./mgmt run --file examples/graph0.yaml --converged-timeout=5 --tmp-prefix` to try out a very simple example!
 * To run continuously in the default mode of operation, omit the `--converged-timeout` option.
 * Have fun hacking on our future technology!
 

resources/file.go

@@ -317,6 +317,7 @@ func (obj *FileRes) Watch(processChan chan event.Event) error {
 
 				// we must be a parent watcher, so descend in
 				if deltaDepth < 0 {
+					// XXX: we can block here due to: https://github.com/fsnotify/fsnotify/issues/123
 					obj.watcher.Remove(current)
 					index++
 				}